The Institute of Electrical and Electronics Engineers (IEEE) 802.1D Spanning-Tree Protocol (STP) standard provides distributed routing over multiple Local Area Networks (LANs) that are connected by bridges. The 802.1D standard is presented in detail in IEEE Standard for Local and Metropolitan Area Networks—Common Specification, Part 3: Media Access Control (MAC) Bridges (The Institute of Electrical and Electronics Engineers, Inc., New York, N.Y. 1998), which is hereby fully incorporated herein by reference. The 802.1D standard was designated at a time where recovering network connectivity within about 60 seconds after an outage was considered as adequate performance. For any network topology changes, the convergence time in the 802.1D standard is usually about 50 seconds (i.e., two times the forward delay plus a maximum age time).
The IEEE 802.1w Rapid Spanning-Tree Protocol (RSTP) standard reduces the convergence time as compared to the 802.1D standard and may be considered as an evolution of the 802.1D standard. The 802.1w standard is presented in detail in IEEE Standard for Local and Metropolitan Area Networks—Common Specification, Part 3: Media Access Control (MAC) Bridges—Amendment 2: Rapid Reconfiguration, (The Institute of Electrical and Electronics Engineers, Inc., New York, N.Y. 2001), which is hereby fully incorporated herein by reference. When a bridge failure or port failure occurs, the RSTP protocol will calculate a new proposal (a loop-free topology) within typically a response time of about 300 milliseconds by deciding which particular ports will be a forwarding port and a blocking port. A port failure can include a link failure or a creation of a new link.
However, there is a need for further enhancements and optimizations to the implementation of the IEEE 802.1w standard.